The coating of woven fabrics with silicone, also termed siliconization, for use in airbags is known to offer the advantage that the hot combustion gases and particles of the propellant charge cannot penetrate the fabric as rapidly, due to the ability of the silicone to absorb heat when the airbag is triggered. Such coatings thereby contribute to protecting the vehicle occupants from possible burns.
Furthermore, a silicone coating reduces the yarn-to-yarn friction produced by vibrations to which the airbag fabric, often enclosed for years in a tight space, is subjected and which can lead to a reduction in the tear resistance.
Finally, the air permeability of the airbag fabric can also be reduced via the silicone coating.
It is evident that the adhesion between the silicone layer and the airbag fabric must be such that, even after years of storage, no peeling of the silicone layer away from the fabric takes place, which would at least severely impair the function of the layer when the airbag is triggered.
Such a coating process is described in EP-A-0,758,666, for example. This publication discloses aqueous, organosiloxane-containing emulsions that are applied to an undried textile.
In accordance with EP-A-0,758,666, the application of the coating material takes place during or directly after the washing process. Particularly suited are synthetic fabrics that must be washed and dried. Care is required that the composition required for coating is applied directly to the still-wet fabric immediately after the washing step and is vulcanized during the drying step.
The coating process according to EP-A-0,758,666 offers the advantage over such processes in the prior art that, when using the organosiloxane-containing emulsions described in this patent, the fabrics can be coated without a preceding drying step, i.e., an additional coating step is no longer necessary after drying and nevertheless the adhesion of the silicone layer to the fabric is improved. Particularly in the case of fabrics made from synthetic fibers, a washing step is regarded as essential.